1. Field of the Invention
The present invention relates to a charging member for use in an electrophotographic apparatus, a process cartridge, and an electrophotographic apparatus.
2. Description of the Related Art
In an electrophotographic apparatus, a roller-shaped charging member (which may hereinafter be referred to as “charging roller”) for charging the surface of an electrophotographic photosensitive member by contacting the surface of the electrophotographic photosensitive member generally has an elastic layer containing a resin. Such charging roller can sufficiently secure a nip width with the electrophotographic photosensitive member, and as a result, can efficiently and uniformly charge the electrophotographic photosensitive member. However, the elastic layer contains a plasticizer or a low-molecular weight component of the resin for softening. Accordingly, the low-molecular weight component may bleed toward the surface of the charging roller owing to long-term use of the roller. To cope with such problem, Japanese Patent Application Laid-Open No. 2001-173641 discloses a conductive roll whose surface is coated with a bleeding inhibition layer made of an inorganic oxide coating formed by a sol-gel method, and suppressing the bleeding of a low-molecular weight component toward the surface thereof.
Investigations conducted by the inventors of the present invention have found that the conductive roll disclosed in Japanese Patent Application Laid-Open No. 2001-173641 whose bleeding inhibition layer serves as a surface layer wears owing to repeated use and hence its charging performance changes over time.